POJ1321 棋盘问题 dfs

Posted 2021-02-07 guaguastandup

太简单了
没啥好说的
存个档

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
typedef long long ll;
const int N=1e9;
int n,k,ans;
string a[9];//map
bool vis[9];//column
void dfs(int x,int step){//current line
    if(step==k){ans++;return;}
    else{
        for(int j=x;j<n;j++){
            for(int i=0;i<n;i++){
                if(a[j][i]=='#'&&!vis[i]){
                    vis[i]=1;
                    dfs(j+1,step+1);
                    vis[i]=0;
                }
            }
        }
    }
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    while(cin>>n>>k){
        if(n==-1)return 0;

        for(int i=0;i<n;i++)cin>>a[i];

        memset(vis,0,sizeof(vis));
        ans=0;

        dfs(0,0);

        cout<<ans<<endl;
    }
return  0;
}